Shift motor actuator circuit

ABSTRACT

A marine propulsion outboard or stern drive includes a motor driven, hydraulic shift mechanism. A DC motor includes the conventional separate reverse winding and forward winding, each of which is connected individually in series with the motor armature to a battery through motor driven limit switches to stop at neutral, forward or reverse drive positions. The armature is connected to drive a valve for actuating a hydraulic shift unit. A resistor and a diode is connected in parallel between the power side of each winding and ground. The resistor acts as an electrical load and eliminates hunting of the drive system and the repeated operation of the limit switches. The resistors employed are relatively low wattage type so as to burn open in a relatively short period and without a flame or mass heat characteristic capable of igniting fuel fumes associated with recreational type marine propulsion devices. The diodes are back biased by the battery polarity but conduct transient voltages of the opposite polarity which may arise in the motor circuit.

United States Patent i [191 Schmiedel 'et al.

[ Dec. 31, 1974 SHIFT MOTORACTUATOR CIRCUIT [75] Inventors: Robert C. Schmiedel, Oshkosh; Richard E. Staerzl, Fond du Lac,

both of Wis. I

[73] Assignee: Brunswick Corporation, Skokie, Ill.

[22] Filed: July 6, 1973 [21] Appl. No.: 377,027

Shimanckas Pervier Primary Examiner-G. Z. Rubinson I Attorney, Agent, or FirmAndrus, Sceales, Starke & Sawall [5 7] ABSTRACT A marine propulsion outboard or stem drive includes a motor driven, hydraulic shift mechanism. A DC motor includes the conventional separate reverse winding and forward winding, each of which is connected individually in series with the motor armature to a battery through motor driven limit switches to stop at neutral, forward or reverse drive positions. ,The armature is connected to drive a valve for actuating a hydraulic shift unit. A resistor and a diode is connected in parallel between the power side of each winding and ground. The resistor acts as an electrical load and eliminates hunting of the drive system and the repeated operation of the limit switches. The resistors employed are relatively low wattage type so as to burn open in a relatively short period and without a flame or mass heat characteristic capable of igniting fuel fumes associated with recreational type marine.

15 Claims, 4 Drawing Figures POWE P- COUPLING CIRCUIT MOTOQ GGAR HY DRAUL 1C SHlFTGR/ e PATENTEDUEB31I9Y4- 3,858.101

NEUTRAL 11592 FORWARD REVERSE SHIFT RANGE SHIFT RANGE REVERSE FORWARD THROTTLE RANGE THROTTLE RANGE 1 'coumsml W I l 1 9 it 1,- MOTOK: GGAR HY omuuc J sHTFTeR/ 1 SHIFT MOTOR ACTUATOR CIRCUIT BACKGROUND OF THE INVENTION This invention relates to a motor energizing circuit and particularly to a direct current motor for driving the shift mechanism of marine propulsion apparatus.

Marine drive systems including outboard motors, stern drive units and the like are widely and advantageously employed, particularly in the recreational boating area. For all but the very smallest outboard type drivers, the throttle and directional controls are located to the forward portion of the boat. Shifting of the drive generally employs mechanical positioning of the gear mechanism in the aft mounted drive apparatus between a neutral position, a forward drive position and a reverse drive position. Conventionally various push-pull cable arrangements have been provided, which mechanically connect the forward located controls to the operating mechanism located in the aft portion of the I boat. An improved electrically coupled shift mechanism for marine propulsion units is disclosed in the copending application of Russel J. Barnes entitled Electrically Controlled Shift Mechanisms for Marine Propulsion Units, which was filed on May 29, 1973, with Ser. No. 364,528 and is assigned to the same assignee as the present application. A plurality of snap action switches are connected to conjointly control and establish anyone of three output signals, each of which is related directly to a corresponding drive position. Thus, the three outputs are uniquely related to the neutral position, the forward drive position, and the reverse drive position. The inputs are applied to a high, speed DC motor shift operator which is responsive to each of the inputs to drive to a preselected position. Thus, the

motor control includes internal switching which establishes the three positions in response to the corresponding inputs to the operator. The shift motor is coupled to set a hydraulic valve system for properly actuating a hydraulic shift mechanism which actually moves a coupling gear between the three positions. The concept of that application has been found to provide a very rapid, reliable and relatively inexpensive shift control. The electrical remote control concept is particularly desirable in that the switch units can be mounted immediately adjacent the forward portion of the control assembly and readily connected through a very simple wiring cable to the aft mounted unit.

For the operation in marine propulsion atmospheres or environments, the systems are generally constructed with fluid tight enclosure means to prevent adverse damaging effect as a result of the high moisture content. Whenever heat sources are included in the mechanism special problems may arise in assuring heat dissipation of a characteristic so as to avoid the generation ,of abnormal damaging heat levels. Thus, in the motor driven control system employing the internal switching means, the high speed drive motor included a tendency for the unit to hunt" as each of the three possible settings was reached. Thus, the shift linkage tended to oscillate about the preset position. Although this did not effect the actual shifting and provided a completely satisfactory establishment of the neutral, forward and reverse gear positions, the oscillations were fed or reflected back into the internal switching mechanism. The switch oscillations tended to create additional actuation of the switches, and relatively rapid breakdown of the limit switches'was encountered. At least part of the problem was found to arise from unacceptable heat levels generated by the increased operation of the limit switches. Thus, the heat levels rose sufficiently to destroy some of the supporting components which permittedexcessive movement of other switch parts. The excessive movement directly contributed to the stresses on the switch elements. Various mechanical means were employed to preload and thereby reduce the speed of the motor armature in order to reduce the oscillating characteristics. Although such systems would improve the life characteristic, they were found to unduly increase the manufacturing process and did not provide a practical or convenient means to modify existing units. Thus, although the remote control motor driven system provides an exceptional satisfactory gear shift mechanism, the normal anticipated life associated with commercially available drives was less than desired, particularly for recreational marine propulsion systems.

SUMMARY OF THE PRESENT INVENTION The present invention is particularly directed to a simple and reliable electrical means for essentially eliminating the hunting characteristic of the driving shift motor and thereby significantly increasing the operating life of the shift control mechanism.

Generally, in accordance with the present invention, an electrical damping circuit means is interconnected to the motor terminals to modify the motor driving characteristics and in particular to essentially eliminate the hunting motor characteristic of the drive unit. More particularly in accordance with the present invention as applied to the direct current drive motor, a resistance damping network is connected across the motor. The resistant elements function as an electrical load which provides compound motor characteristics decreasing the no-load speed of the motor. Further, the resistance elements act to create dynamic braking in the event the motor is functioning to generate power. Further, applicants analysis noted the creation of negative voltage spikes or signals generated within the motor which appear to adversely affect the desired smooth operation of the motor drive. Applicant has found that such extraneous signals are reliably eliminated by connecting of properly polarized diode means in parallel with the modifying resistant means and the motor.

In a particularly novel aspect and feature of the present invention, the DC motor includes the conventional separate reverse winding and forward winding each of which is connected individually in series with the armature. The power is applied across the appropriate winding, and armature in series through the motor driven limit switches. A resistor and a diode are connected in parallel between the power side of each winding and ground. Applicants found that with this modification the adverse hunting characteristic of the system was completely eliminated. Although the shift time was increased slightly, it was not considered in any way significant from a practical standpoint. Similarly, the peak amperage drawn by the circuit increased but once again was clearly within satisfactory practical limits. Further, in the event of an abnormal mechanical condition, such as a shift linkage locking or jamming against movement, the applied voltage appears directly across the resistor to the ground. The resistors employed are relatively low wattage type and under such conditions, burn open in a relatively short period. However, there is no flame or mass heat characteristic and consequently there is no danger of an explosive heat source created. If the linkage is unjammed, the motor continues to operate to provide shifting although the hunting characteristic is encountered with a reduction in the life unit.

The present invention, thus, provides a relatively simple and inexpensive means for creating a stable electric motor driven shifting mechanism with an improved life and one which is particularly adapted to modification of presently existing units as well as the use of mass produced motors for initial manufacture of the shift control drive.

BRIEF DESCRIPTION OF DRAWINGS In the drawing,

FIG. 1 is a diagrammatic illustration of a control system for a marine propulsion unit with an electrically responsive remote shift control.

FIG. 2 is a schematic illustration of a drive motor and associated dampened circuit constructed in accordance with the present invention.

FIG. 3 is a typical illustration of a motor characteristic without the damping modification shown in FIG. 2, and;

FIG. 4 is a typical characteristic of the motor with the electrical damping circuit of FIG. 1.

DESCRIPTION OF ILLUSTRATED EMBODIMENT Referring to the drawings and particularly to FIG. 1, the present invention is illustrated in connection with a shifting control for a stern drive unit 1 secured to the aft end of a boat 2. A single lever control unit 3 is mounted in the forward portion of the boat and connected through a suitable coupling cable 4 to actuate a motor driven shift mechanism or unit 5. The cable 4 is an electrical cable providing connection between control switches 6 mounted in forward control unit 3 for selectively supplying power to anyone of three inputs to the motor driven shift unit 5. The switching system may for example be constructed as taught and shown in the previously referred to copending application of Barnes.

Referring particularly to FIG. 2, the shift unit includes a direct current motor 7 which for marine outboard and/or stern drive units may typically be a 12 volt motor. The motor 7 includes an armature 8 which is coupled to position a hydraulic valve 9 for affecting movement of the shift linkage and gear mechanism 10. A forward field winding 11 is connected in series with the armature 8 to create energization of the motor 7, with the armature rotating in the direction placing the valve 9 in a forward drive position. Thus, the one side of the armature 8 is grounded and the opposite side is connected in series with the forward winding 11 to a forward limit switch 12 of a switch assembly which is connected through a coupling circuit to a battery 13. A reverse winding 14 is similarly connected between the ungrounded side of the armature 8 and a reverse switch 15 of the limit switch assembly. Energization through the reverse winding 14 results in a corresponding opposite rotation of the armature 8 and placement of valve 9 in the reverse drive position.

The deenergization of the circuits of forward and reverse winding 11 and 14 is selectively controlled by the limit switches 12 and 15. Thus, the motor armature 8 opens the corresponding switch when each position is reached. The switches are connected to power through a coupling circuit 16 which is controlled by the input switches 6 of the forward by located control unit 3 to provide energization of one of the windings 11 and 14 to drive the armature 8 until the desired position is established. An internal switch, not shown, provides for the neutral position. Any suitable interconnecting circuit can of course be employed which employs motorcoupled limit switches. For example, a motor-limit switch unit manufactured and sold by Prestolite Company, a division of Ultra Corporation has been satisfactorily employed. No further detailed illustration or description thereof is given as any other suitable switching system can be readily developed by those skilled in the art. In such constructions it will be found that the drive motor and the interconnected mechanical system tends to cause hunting of the system with the mechanical oscillation resulting in additional activation of the limit switches 12 and 15 about the set stop position. Thus, if the drive unit tends to hunt at the desired position, the switch assembly will operate sequentially. In actual practice, a characteristic of voltage applied to the motor winding versus time such as shown in FIG. 3 was obtained. Thus, assuming switch 12 is closed, energy is being applied to the the motor winding 11. At time or point one 17 the limit switch 12 was momentarily closed to again apply power across the motor 7 as shown by the transient voltage signal 19. A short period of time thereafter, a second transient switching condition as shown at 20 occurred and only then did the motor 7 energization terminate and remain off. This type of switching characteristic was repeated with each shifting and, as previously noted, particularly contributed to a significant reduction in the operating life of the unit.

In accordance with the present invention, similar damping circuits 21 and 22 are connected, one each, between the input of each of the reverse and forward windings 11 and 14 to ground and thus across the operating motor circuit for each direction. Each of the damping circuits 21 and 22 is identical and consequently that for the forward winding 11 is described in detail.

The dampening circuit 21 first includes a small resistor 23 connected at one end between the junction of switch 12 and the winding 11 and the opposite end to ground. Resistor 23 is directly in parallel with the series connected forward winding 11 and the armature 8. Further, in parallel with the dampening resistor 23 and thus also across the series connected forward winding 11 and armature 8, a high voltage, low amperage diode 24 is connected. The diode 24 is connected with its anode connected to ground and its cathode connected to the power or positive side of the forward winding 11 such that the diode 24 is reverse biased with respect to the applied voltage and thus does not normally conduct. Any negative voltage signals or transients generated within the motor 7 however forward biases the diode 24, which presents a relatively low resistance for such signals and are readily conducted by the diode. Thus, the diode for a typical l2-volt motor is 1,000 volt-amp diode.

Applicant has found that applied to a marine propulsion control unit with an impressed voltage of between 12 and 14.8 volts, there was no hunting as the mechanism was driven to anyone of the 3 positions. The char acteristic of the drive motor 7 changes from the characteristic shown in FIG. 3 to a characteristic such as typically shown in FIG. 4. Thus, the power trace 25 impressed upon the motor changes at the time of switching from the full power to essentially zero power, instantaneously as at 26, without any reapplication. This clearly indicates the essentially complete elimination of the hunting characteristics such to cause the transient switch operation as previously discussed. The shift time was increased from approximately 0.05 to 0.08 seconds. Further, the peak amperage requirements was increased from approximately 9 /2 to amperes. Neither operating condition adversely affects the functioning of the system from a practical standpoint. The damping circuit did result in a very significant increase in the operating life of the unit, and has the further distinct advantage of being readily and conveniently applied to existing designed motor drive systems including the limit switch units.

The drive motor and limit switch unit is often mounted within an enclosure. In ignition systems for marine propulsion devices and the like, special care is therefore normally taken to prevent the possibility of damage heat energy with a generation of potentially explosive condition resulting from an accumulation of fuel fumes which in the presence ofa spark could cause an explosion. In accordance with this invention, resistors 23 and 23' are selected as low wattage resistors so to prevent prolonged significant heat generation even in the presence of a locked motor condition. Thus, in the event the shift linkage should jam and lock the motor armature 8 against rotation, full voltage is applied directly across a resistor 23 or 23' to ground. In

a practical installation, a three ohm five watt resistor was employed. A l2-volt battery impressed across the low wattage resistor causes the resistor to rapidly burn open and with the prescribed values in approximately 15-20 seconds. However, there is no flame nor any significant mass heat. Consequently, the heated resistor 23, or 23' does not in any way create a dangerous condition when applied to marine propulsion devices.

If the linkage or other holding means corrects itself and is unjammed after the resistor 23 or 23 burns out, the motor 7 will of course continue to operate but with the conventional hunting characteristic for the one direction, as previously discussed, because the damping We claim:

1. A marine propulsion apparatus having a shift mechanism movable between plurality of drive positions by an electrically driven actuator having limit switches actuated at each of the said positions to terminate operation of the actuator, said actuator comprising an electrical drive means having a power input means connected in circuit with said limit switches,

said actuator having means tending to produce oscillation about each driven position and thereby produce an oscillatory switch operation in response to establishing of said drive positions, said oscillatory switch operation functioning to significantly reduce the life of the actuator, and an electrical dampening circuit means connected in parallel with said electrical drive means and selected to prevent said oscillatory switch operation.

2. The marine propulsion apparatus of claim I wherein said dampening circuit means includes relatively low wattage resistors means and burning open with essentially zero watt level to prevent creation of heat energy capable of igniting gasoline fumes.

3. In the marine propulsion apparatus of claim I wherein said drive means is a direct current motor and said dampening circuit means includes a resistor means in parallel with a diode means, said diode means being connected to conduct transient voltage signals developed within said drive means.

4. The marine propulsion apparatus of claim 1 wherein said drive means includes a direct current motor means having an armature and a pair of paralleled windings connected in circuit with said limit switches, a control linkage coupled to said armature and said electrical dampening circuit means, including a first resistor connected in parallel with said armature and a first of said windings and including a second resistor connected in parallel with the armature, and the second of said windings, said resistors being selected to prevent said oscillatory switch operation.

5. The marine propulsion apparatus of claim 4 having a battery power supply of a selected maximum output voltage wherein said first and second resistors have a wattage rating less than that established with the full voltage applied directly across one of said resistors.

6. In a marine propulsion apparatus having a shift mechanism movable between a neutral position, a forward drive position and a reverse drive position by an electrically driven actuator having limit switches actuated at each of the said positions to terminate operation of the actuator, said actuator comprising an electrical drive means having a power input means connected in circuit with said limit switches, said actuator having means tending to produce oscillation about each driven position and thereby produce an oscillatory switch operation in response to establishing of said shift posi tions, said oscillatory switch operation functioning to significantly reduce the life of the actuator, and an electrical dampening circuit means connected in parallel with said electrical drive means and selected to prevent said oscillatory switch operation.

7. In the marine propulsion apparatus of claim 6 wherein said dampening circuit means includes a resistance means of a relative low wattage rating and burning open with essentially a zero heat level to essentially completely eliminate the capability of igniting gasoline fumes.

8. In the marine propulsion apparatus of claim 6 wherein said dampening circuit means includes a diode means connected to conduct transient voltage signals developed within said drive means. i

9. The marine propulsion apparatus of claim 6 wherein said electrical drive means includes a direct current motor means having winding means connected in circuit with said limit switches, said electrical dampening circuit means being connected in parallel with said winding means.

10. The marine propulsion apparatus of claim 9 wherein said direct current motor means includes an armature connected in a first series circuit with a forward winding means and in a second series circuit with a reverse winding means and each circuit connected to one of said limit switches, said electrical dampening means including a pair of circuit means connected one each in parallel with each of said series circuits and in series with the corresponding limit switches.

11. in the marine propulsion apparatus of claim 10 wherein each of said dampening circuit means includes a resistor means in parallel with a diode means.

12. The marine propulsion apparatus of claim 11 wherein each resistance means has relative low wattage rating and burning open with essentially a zero heat level to essentially completely eliminate the capability of igniting gasoline fumes.

13. The marine propulsion apparatus of claim 6 wherein said shift mechanism includes a hydraulic actuator having a mechanical valve means for establishing the shift positions and said drive means includes a direct current motor means having an armature and a pair of paralleled windings connected in circuit with said limit switches, a linkage coupling said armature to said valve means, and said electrical dampening circuit means including a first resistor connected in parallel with said armature and a first of said windings and including a second resistor connected in parallel with the armature, and the second of said windings, said resistors being selected to prevent said oscillatory switch operation.

14. The marine propulsion apparatus of claim 13 wherein said dampening circuit means includes first and second diode means connected in parallel one each with said first and second resistors to conduct transient voltage signals developed with said motor means.

15. The marine propulsion apparatus of claim 13 having a battery power supply of a selected maximum output voltage wherein said first and second resistors are a wattage rating less than that established with the full voltage applied directly across one of said resistors.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,858,101 Dated December 31, 1974 Inventor(s) Robert C. Schmiedel and Richard E. Staerzl It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line ll, cancel "drivers" and substitute therefor ---drives---, column 4, line 20, cancel "12 and 15" and substitute therefor ---l2, l5 and l6---, column 6, line 24, after "armature" insert (a comma) column 6, line 25, after 'means" cancel (a comma) column 6, line 28, after "armature" cancel (a comma).

Signed and sealed this 1st day of April 1.975.

EAL) fittest:

C. I-LARSEL- IL DAI-II? Commissioner of. Patents and Trademarks Attesting Officer FORM PO-105O (10-69) USCOMM'DC OOS'IB-PGO fl' U.S. GOVERNMENT PRINTING OFFICE I! 0-3i-SSI,

UNITED STATES PATEIIT OFFICE CERTIFICATE OF CORRECTION Patent No- 3,858,l0l Dated December 31, 1974 Inventor(s) Robert C. Schmiedeland Richard E. Staerzl It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line ll, cancel "drivers" and substitute therefor ---drives---, column 4, line 20, cancel "l2 and 15'' and substitute therefor --l2, l5 and l6---, column 6, line 24, after "armature" insert (a comma), column 6, line 25, after "means" cancel (a comma) column 6, line 28, after "armature" cancel (a comma).

Signed and sealed this let day of April 1975.

SEAL) An st:

C. I-iARSHALL DAI-II? "II-3 C 31 K383 Cozwnissioner of Patents attesting Oifzcer and Tra m FORM PO-105O (10-69) USCOMM-DC 60370?" u.s. GOVIIIIIIII'I manna omcl no o-au-su, 

1. A marine propulsion apparatus having a shift mechanism movable between plurality of drive positions by an electrically driven actuator having limit switches actuated at each of the said positions to terminate operation of the actuator, said actuator comprising an electrical drive means having a power input means connected in circuit with said limit switches, said actuator having means tending to produce oscillation about each driven position and thereby produce an oscillatory switch operation in response to establishing of said drive positions, said oscillatory switch operation functioning to significantly reduce the life of the actuator, and an electrical dampening circuit means connected in parallel with said electrical drive means and selected to prevent said oscillatory switch operation.
 2. The marine propulsion apparatus of claim 1 wherein said dampening circuit means includes relatively low wattage resistors means and burning open with essentially zero watt level to prevent creation of heat energy capable of igniting gasoline fumes.
 3. In the marine propulsion apparatus of claim 1 wherein said drive means is a direct current motor and said dampening circuit means includes a resistor means in parallel with a diode means, said diode means being connected to conduct transient voltage signals developed within said drive means.
 4. The marine propulsion apparatus of claim 1 wherein said drive means includes a direct cUrrent motor means having an armature and a pair of paralleled windings connected in circuit with said limit switches, a control linkage coupled to said armature and said electrical dampening circuit means, including a first resistor connected in parallel with said armature and a first of said windings and including a second resistor connected in parallel with the armature, and the second of said windings, said resistors being selected to prevent said oscillatory switch operation.
 5. The marine propulsion apparatus of claim 4 having a battery power supply of a selected maximum output voltage wherein said first and second resistors have a wattage rating less than that established with the full voltage applied directly across one of said resistors.
 6. In a marine propulsion apparatus having a shift mechanism movable between a neutral position, a forward drive position and a reverse drive position by an electrically driven actuator having limit switches actuated at each of the said positions to terminate operation of the actuator, said actuator comprising an electrical drive means having a power input means connected in circuit with said limit switches, said actuator having means tending to produce oscillation about each driven position and thereby produce an oscillatory switch operation in response to establishing of said shift positions, said oscillatory switch operation functioning to significantly reduce the life of the actuator, and an electrical dampening circuit means connected in parallel with said electrical drive means and selected to prevent said oscillatory switch operation.
 7. In the marine propulsion apparatus of claim 6 wherein said dampening circuit means includes a resistance means of a relative low wattage rating and burning open with essentially a zero heat level to essentially completely eliminate the capability of igniting gasoline fumes.
 8. In the marine propulsion apparatus of claim 6 wherein said dampening circuit means includes a diode means connected to conduct transient voltage signals developed within said drive means.
 9. The marine propulsion apparatus of claim 6 wherein said electrical drive means includes a direct current motor means having winding means connected in circuit with said limit switches, said electrical dampening circuit means being connected in parallel with said winding means.
 10. The marine propulsion apparatus of claim 9 wherein said direct current motor means includes an armature connected in a first series circuit with a forward winding means and in a second series circuit with a reverse winding means and each circuit connected to one of said limit switches, said electrical dampening means including a pair of circuit means connected one each in parallel with each of said series circuits and in series with the corresponding limit switches.
 11. In the marine propulsion apparatus of claim 10 wherein each of said dampening circuit means includes a resistor means in parallel with a diode means.
 12. The marine propulsion apparatus of claim 11 wherein each resistance means has relative low wattage rating and burning open with essentially a zero heat level to essentially completely eliminate the capability of igniting gasoline fumes.
 13. The marine propulsion apparatus of claim 6 wherein said shift mechanism includes a hydraulic actuator having a mechanical valve means for establishing the shift positions and said drive means includes a direct current motor means having an armature and a pair of paralleled windings connected in circuit with said limit switches, a linkage coupling said armature to said valve means, and said electrical dampening circuit means including a first resistor connected in parallel with said armature and a first of said windings and including a second resistor connected in parallel with the armature, and the second of said windings, said resistors being selected to prevent said oscillatory switch operation.
 14. The marine propulsion apparatus of claim 13 wherein said dampening circuiT means includes first and second diode means connected in parallel one each with said first and second resistors to conduct transient voltage signals developed with said motor means.
 15. The marine propulsion apparatus of claim 13 having a battery power supply of a selected maximum output voltage wherein said first and second resistors are a wattage rating less than that established with the full voltage applied directly across one of said resistors. 